Convenient preparation of Li[(η5-C5Me5)M(CO)2] (M = Ru, Fe) by the reaction of (η5-C5Me5)M(CO)2H with n-BuLi

Article abstract of DOI:10.1016/S0022-328X(01)01373-0

The anionic ruthenium and iron complexes Li[(η⁵-C₅Me₅)M(CO)₂] (M = Ru (1-Ru), Fe (1-Fe)) were generated by deprotonation of the transition metal hydride (η⁵-C₅Me₅)M(CO)₂

Full text of DOI:10.1016/S0022-328X(01)01373-0

Journal of Organometallic Chemistry 645 (2002) 201–205
www.elsevier.com/locate/jorganchem
Convenient preparation of Li[(h5-C5Me5)M(CO)2] (M=Ru, Fe) by
the reaction of (h5-C5Me5)M(CO)2H with n-BuLi
Masaaki Okazaki *, Kazuyuki Satoh, Tadahiro Akagi, Masatoshi Iwata,
Kyeong A Jung, Rie Shiozawa, Hiroshi Okada, Keiji Ueno, Hiromi Tobita *,
Hiroshi Ogino
Department of Chemistry, Graduate School of Science, Tohoku Uni6ersity, Sendai 980-8578, Japan
Received 16 August 2001; received in revised form 9 October 2001; accepted 12 October 2001
Abstract
The anionic ruthenium and iron complexes Li[(h5-C5Me5)M(CO)2] (M=Ru (1-Ru), Fe (1-Fe)) were generated by deprotonation
of the transition metal hydride (h5-C5Me5)M(CO)2H with n-BuLi in tetrahydrofuran (THF). The reaction proceeded at −45 °C
immediately. Reactions of 1 with various electrophiles (Me3SiCl, pTol2HSiCl, Me2SiCl2, MeSiCl3, SiCl4, Me3SiSiMe2Cl, and
Ph2GeCl2) afforded the corresponding nucleophilic substitution products (h5-C5Me5)M(CO)2ER3 (E=Si, Ge) via salt-elimination.
© 2002 Elsevier Science B.V. All rights reserved.
Keywords: Anionic complex; Silyl complex; Germyl complex; Deprotonation; Salt-elimination
1. Introduction
type (h5-C5H5)M(CO)2ERn (M=Fe, Ru, ERn=H,
CR3, SiR3, GeR3) [1,2]. Upon photolysis, these com-
plexes can easily be converted into the coordinatively
unsaturated complexes (h5-C5H5)M(CO)ERn via disso-
ciation of a carbonyl ligand. This simple reaction opens
up rich chemistry. For example, irradiation of (h5-
C5H5)Fe(CO)2SiMe2SiMeR2 (R=Me, Et, Ph) gives a
mixture of monosilyliron complexes (h5-C5H5)Fe(CO)2-
SiMe3−nRn (n=0–2), with scrambling of alkyl and
aryl groups on the silicon atoms (Scheme 1) [5,6]. The
reaction is assumed to proceed via the formation of a
silyl(silylene)iron intermediate and the subsequent rapid
intramolecular 1,3-migration from the silyl group to the
silylene ligand. Actually, when the photoreaction is
performed in the presence of the intramolecular donor
such as alkoxy or amino groups, the donor-bridged
bis(silylene) complexes are formed almost quantitatively
Eq. (1) [7]. The methoxy-bridged bis(silylene) ruthe-
nium complex can also be isolated in the same manner
The anionic transition-metal complexes [(h5-
C5R5)M(CO)2]− (R=H, Me, M=Ru, Fe) have widely
been recognized as versatile synthons for synthesis of
Group 8 transition-metal complexes [1,2]. Reduction of
[(h5-C5H5)M(CO)2]2 (M=Ru [4], Fe [1a,3]) by using
Na–K alloy or sodium amalgam is a conventional
route to the anions [(h5-C5H5)M(CO)2]−. Treatment of
the anions with electrophiles affords complexes of the
Eq. (2) [2c,2d].
(1)
Scheme 1.
* Corresponding authors. Tel.: +81-22-2176541; fax: +81-22-
2176543.
E-mail address: tobita@inorg.chem.tohoku.ac.jp (H. Tobita).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01373-0

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M. Okazaki et al. / Journal of Organometallic Chemistry 645 (2002) 201–205
character and steric hindrance. Malisch et al. reported
that the reduction of [(h5-C5Me5)Ru(CO)2]2 with Na–K
alloy proceeded almost quantitatively to generate [(h5-
C5Me5)Ru(CO)2]− [2a]. This synthetic method of the
ruthenium anion, however, has not commonly been
used, because it requires very long time (3 days) for
reduction and the resulting anion decomposes easily
during the filtration for removal of Na–K alloy. In the
previous paper, we developed a versatile method for the
generation of the osmium anion [(h5-C5Me5)Os(CO)2]−
by the reaction of (h5-C5Me5)Os(CO)2H with n-BuLi
[8]. This paper describes application of the method for
the generation of the ruthenium and iron anions [(h5-
C5Me5)M(CO)2]− (M=Ru, Fe) in which the procedure
such as filtration to remove excess reducing agent is not
necessary.
2. Results and discussion
To a pale yellow tetrahydrofuran (THF) solution of
the hydridoruthenium complex (h5-C5Me5)Ru(CO)2H
was added 1.1 equivalents of n-BuLi at −45 °C. The
color of the solution changed to greenish brown imme-
diately. Subsequent addition of excess Me3SiCl in THF
gave a red solution from which trimethylsilyl complex
(h5-C5Me5)Ru(CO)2SiMe3 (2) was isolated in 84%
yield. Similarly, the reactions of the greenish brown
solution with various chlorosilanes afforded the corre-
sponding silyl complexes (3–6) (Scheme 2). In these
reactions, the first step is considered to be deprotona-
tion of the ruthenium hydride leading to generation of
the ruthenium anion [(h5-C5Me5)Ru(CO)2]− (1-Ru).
The elemental analysis and spectroscopic data of the
products 2–6 (Table 1) fully support the structures
illustrated in Scheme 2. In the reactions of the ruthe-
nium anion 1-Ru with MeSiCl3 and SiCl4, the forma-
tion yields of the silylruthenium complexes 5 and 6
were quite low. In these cases, formation of a consider-
able amount of (h5-C5Me5)Ru(CO)2Cl was observed.
Scheme 2. Generation and reactions of Li[(h5-C5Me5)Ru(CO)2] (1-
Ru).
(2)
Recently, the pentamethylcyclopentadienyl ancillary
ligand (h5-C5Me5) has widely been used, because it is
recognized that the h5-C5Me5 ligand stabilizes most of
the organometallic complexes by its electron-releasing
Table 1
Elemental analysis, IR, and mass spectral data for ruthenium and iron complexes
Complex
Anal. Found (Calc.) (%)
IR (cm−1
)
Mass (EI, 70 eV), m/z
C
H
(wCO)
Cp*Ru(CO)2SiMe3 (2)
Cp*Ru(CO)2SipTol2H (3)
Cp*Ru(CO)2SiMe2Cl (4)
Cp*Ru(CO)2SiMeCl2 (5)
Cp*Ru(CO)2SiCl3 (6)
Cp*Ru(CO)2SiMe2SiMe3 (7)
Cp*Ru(CO)2GePh2Cl (8)
Cp*Fe(CO)2SiMe2Cl (9)
49.33 (49.29)
61.71 (62.00)
43.90 (43.57)
38.57 (38.43)
34.64 (33.77)
47.88 (48.22)
51.94 (51.98)
49.46 (49.35)
6.39 (6.62)
5.82 (6.00)
5.36 (5.49)
4.44 (4.46)
3.52 (3.52)
7.18 (7.09)
4.47 (4.54)
6.07 (6.21)
1992, 1923
1992, 1932
1996, 1944
2015, 1963
2035, 1984
1990, 1932
1996, 1942
1978, 1928
366 (M+, 59), 292 (M+ꢀSiMe3, 100)
504 (M+, 3), 447 (M+ꢀ2COꢀH, 100)
386 (M+, 24), 330 (M+ꢀ2CO, 100)
406 (M+, 20), 236 (M+ꢀSiMeCl2ꢀ2CO, 100)
426 (M+, 16), 236 (M+ꢀSiCl3ꢀ2CO, 100)
424 (M+, 24), 351 (M+ꢀSiMe3, 100)
554 (M+, 12), 526 (M+ꢀCO, 100)
340 (M+, 26), 284 (M+ꢀ2CO, 100)

M. Okazaki et al. / Journal of Organometallic Chemistry 645 (2002) 201–205
203
Disilanyl complex (h5-C5Me5)Ru(CO)2SiMe2SiMe3
(7) can also be synthesized in 92% yield by the reaction
of 1-Ru with Me3SiSiMe2Cl. The 29Si resonances of the
disilanyl ligand appear at −1.7 and −13.1 ppm.
Treatment of the ruthenium anion with Ph2GeCl2
afforded germylruthenium complex 8 as shown in
Scheme 2. The elemental analysis and spectroscopic
data are consistent with the formation of the germyl
complex 8.
(1-Ru), Fe (1-Fe)) by the reaction of (h5-
C5Me5)M(CO)2H with n-BuLi have been established.
Some new ruthenium(II) and iron(II) complexes with a
h5-C5Me5 ancillary ligand (h5-C5Me5)M(CO)2ER3 were
prepared by the reactions of the anions 1-Fe and 1-Ru
with electrophiles.
3. Experimental
The silyliron complex (h5-C5Me5)Fe(CO)2SiMe2Cl
was obtained by a procedure similar to that for the
ruthenium analog. Thus, treatment of the hydridoiron
complex (h5-C5Me5)Fe(CO)2H with 1.1 equivalents of
n-BuLi at −45 °C in THF gave a deep red solution of
1-Fe. Subsequent addition of Me2SiCl2 and workup
gave the silyliron complex (h5-C5Me5)Fe(CO)2SiMe2Cl
(9) in 89% yield (Eq. (3)).
3.1. General comments
All manipulations were carried out under a dry nitro-
gen or argon atmosphere. Reagent-grade THF, toluene,
hexane, and pentane were distilled from sodium-ben-
zophenone immediately before use. Benzene-d6 was
dried over molecular sieves 4A. The compounds (h5-
C5Me5)Ru(CO)2H [10], (h5-C5Me5)Fe(CO)2H [11],
Me3SiSiMe2Cl [12], HpTol2SiCl [13], and Ph2GeCl2 [14]
were prepared according to published procedures. All
other chemicals were used as received. All NMR spec-
tra were recorded on a Bruker ARX-300 spectrometer.
The IR spectra were recorded on Bruker IFS66v and
Horiba FT-200 spectrophotometers. Mass spectra were
obtained with a JEOL JMS-HX110 spectrometer. The
elemental analysis data and IR and MS data for com-
pounds were summarized in Table 1.
(3)
We reported previously the generation and character-
ization of osmium anion [(h5-C5Me5)Os(CO)2]− by the
reaction of (h5-C5Me5)Os(CO)2H with n-BuLi, which
reacted with various electrophiles to give the nucle-
ophilic substitution products [8]. We applied this
preparative method of [(h5-C5Me5)Os(CO)2]− for syn-
thesis of the ruthenium and iron analogs, and suc-
ceeded in removing the following difficulties
accompanying the conventional methods.
3.2. Synthesis of (p5-C5Me5)Ru(CO)2SiMe3 (2)
To a THF (50 ml) solution of (h5-C5Me5)Ru(CO)2H
(846 mg, 2.88 mmol) was added n-BuLi (1.58 M, 2.7
ml, 4.3 mmol) at −45 °C (CH3CN–liquid N2 bath).
After stirring the mixture for 30 min, a THF (20 ml)
solution of Me3SiCl (472 mg, 4.34 mmol) was added to
the solution at −45 °C. The mixture was stirred for 30
min at −45 °C and then warmed up to room tempera-
ture (r.t.) and stirred for 1 h. After removal of volatiles
under vacuum, the residue was extracted with hexane
and the extract was filtered through the Celite pad.
Removal of solvent from the filtrate under reduced
1. Preparation of [(h5-C5Me5)M(CO)2]− (M=Ru, Fe)
by a conventional method, i.e. reduction of the
dimer [(h5-C5Me5)M(CO)2]2 with metal reducing
agents takes long time [2–4 h (M=Fe, potassium
mirror or sodium amalgam [1e,9])], 3 days (M=
Ru, Na–K mirror [2a]). In contrast, the reaction of
(h5-C5Me5)M(CO)2H with n-BuLi proceeds instan-
taneously at −45 °C.
2. In the conventional method, the reducing agent
such as Na–K alloy should be removed before the
anion [(h5-C5Me5)M(CO)2]− is served for the subse-
quent reaction. A usual method is the filtration of
the extremely air- and moisture-sensitive solution of
the anion. But, this procedure sometimes leads to
decomposition of the anion by air-oxidation to give
the dimer [(h5-C5Me5)M(CO)2]2. A special experi-
mental skill is required for the conventional
method. In contrast, the reaction of (h5-
C5Me5)M(CO)2H with n-BuLi requires no subse-
quent procedure such as filtration, and the reaction
mixture can immediately be used for the next
reaction.
pressure afforded
a
brown powder of (h5-
C5Me5)Ru(CO)2SiMe3 (2; 880 mg, 2.41 mmol, 84%).
Analytically pure sample was obtained by recrystalliza-
tion from hexane at −30 °C. 1H-NMR (300 MHz,
C6D6) l 0.60 (s, 9H, SiMe3), 1.60 (s, 15H, C5Me5).
13C{1H}-NMR (75.5 MHz, C6D6) l 6.8 (SiMe3), 10.3
(C5Me5), 99.2 (C5Me5), 204.7 (2CO). 29Si{1H}-NMR
(59.6 MHz, C6D6) l 25.7.
3.3. Synthesis of (p5-C5Me5)Ru(CO)2SipTol2H (3)
Compound 3 was synthesized by a similar method to
that for 2, using (h5-C5Me5)Ru(CO)2H (680 mg, 2.32
mmol) and pTol2SiHCl (1.20 g, 4.86 mmol). The residue
was extracted with hexane (60 ml) and the extract was
In conclusion, a new convenient route to the ruthe-
nium and iron anions [(h5-C5Me5)M(CO)2]− (M=Ru

204
M. Okazaki et al. / Journal of Organometallic Chemistry 645 (2002) 201–205
filtered through a Celite pad. The filtrate was evapo-
rated to dryness and the residue was recrystallized from
pentane to give C5Me5Ru(CO)2SipTol2H (3) (613 mg,
mmol) in 19% yield. Recrystallization from hexane at
−30 °C gave colorless needles of 6. 1H-NMR (300
MHz, C6D6) l 1.44 (s, 15H, C5Me5). 13C{1H}-NMR
(75.5 MHz, C6D6) l 9.5 (C5Me5), 101.2 (C5Me5), 199.6
(2CO).
1
1.22 mmol, 53%) as pale yellow crystals. H-NMR (300
MHz, C6D6) l 1.52 (s, 15H, C5Me5), 2.11 (s, 6H,
p-C6H5CH3), 5.56 (s, 1H, SiH), 7.08–7.10, 7.89–7.91
(AB q, J=8 Hz, 4H×2, Ar). 13C{1H}-NMR (75.5
MHz, C6D6) l 9.71 (C5Me5), 21.4 (p-C6H5CH3), 99.2
(C5Me5), 129.1, 135.6, 137.6, 139.0 (Ar), 204.3 (2CO).
29Si{1H}-NMR (59.6 MHz, C6D6) l 23.9. IR (KBr
pellet) 2052 cm−1 (wSiꢀH).
3.7. Synthesis of (p5-C5Me5)Ru(CO)2SiMe2SiMe3 (7)
Compound 7 was synthesized by a similar method to
that for 2, using (h5-C5Me5)Ru(CO)2H (658 mg, 2.25
mmol) and Me3SiSiMe2Cl (562 mg, 3.38 mmol).
Volatiles were removed under reduced pressure from
the resulting mixture. The residue was extracted with
hexane and the extract was filtered through the Celite
pad. Removal of the solvent from the extract under
reduced pressure afforded an orange oil of 7 (880 mg,
2.08 mmol, 92% yield). Further purification by
medium-pressure liquid chromatography on silica-gel
(hexane as eluent) afforded an analytical pure sample of
3.4. Synthesis of (p5-C5Me5)Ru(CO)2SiMe2Cl (4)
Compound 4 was synthesized by a similar method to
that for 2, using (h5-C5Me5)Ru(CO)2H (496 mg, 1.69
mmol) and Me2SiCl2 (662 mg, 5.13 mmol). The reaction
mixture was subjected to a silica gel flash column and
elution was carried out with a toluene–hexane (1:2)
mixture. Evaporation of the fraction to dryness af-
forded colorless crystals of 4 in 73% yield (474 mg, 1.23
mmol). 1H-NMR (300 MHz, C6D6) l 0.93 (s, 6H,
SiMe2), 1.58 (s, 15H, C5Me5). 13C{1H}-NMR (75.5
MHz, C6D6) l 10.0 (SiMe2), 12.1, (C5Me5), 100.3
(C5Me5), 202.9 (2CO). 29Si{1H}-NMR (59.6 MHz,
C6D6) l 69.9.
1
7 (colorless oil). H-NMR (300 MHz, C6D6) l 0.37 (s,
6H, SiMe2), 0.63 (s, 9H, SiMe3), 1.60 (s, 15H, C5Me5).
13C{1H}-NMR (75.5 MHz, C6D6) l 0.5, 2.7 (SiMe),
10.4 (C5Me5), 99.9 (C5Me5), 204.7 (2CO). 29Si{1H}-
NMR (59.6 MHz, C6D6) l −13.1, −1.7.
3.8. Synthesis of (p5-C5Me5)Ru(CO)2GePh2Cl (8)
Compound 8 was synthesized by a similar method to
that for 2, using (h5-C5Me5)Ru(CO)2H (497 mg, 1.69
mmol) and Ph2GeCl2 (0.80 g, 2.69 mmol). The reaction
mixture was placed on a silica-gel flash column and
elution was carried out with a toluene–hexane (1:1)
mixture. Removal of solvent from the fraction afforded
a light yellow powder of 8 (639 mg, 1.15 mmol) in 68%
yield. 1H-NMR (300 MHz, C6D6) l 1.48 (s, 15H,
C5Me5). 7.09, 7.22, 7.97 (m, Ph2). 13C{1H}-NMR (75.5
MHz, C6D6) l 9.8 (C5Me5), 100.1 (C5Me5), 128.2,
128.7, 133.3, 146.6 (Ph2), 202.7 (2CO).
3.5. Synthesis of (p5-C5Me5)Ru(CO)2SiMeCl2 (5)
Compound 5 was synthesized by a similar method to
that for 2, using (h5-C5Me5)Ru(CO)2H (400 mg, 1.36
1
mmol) and MeSiCl3 (0.32 g, 2.5 mmol). The H-NMR
spectrum revealed that the resulting mixture contains 5
and (h5-C5Me5)Ru(CO)2Cl in the molar ratio of 1:2.7.
The reaction mixture was subjected to a silica gel flash
column and elution was carried out with a toluene–
hexane (1:9) mixture. Removal of solvent from the
fraction afforded a white powder of 5 in 27% yield (150
mg, 0.369 mmol). Recrystallization from hexane at
−30 °C gave colorless needles of 5. 1H-NMR (300
MHz, C6D6) l 1.26 (s, 3H, SiMe), 1.54 (s, 15H, C5Me5).
13C{1H}-NMR (75.5 MHz, C6D6) l 9.7 (C5Me5), 17.9
(SiMe) 101.0 (C5Me5), 201.2 (2CO). 29Si{1H}-NMR
(59.6 MHz, C6D6) l −21.4.
3.9. Synthesis of (p5-C5Me5)Fe(CO)2SiMe2Cl (9)
To a THF (20 ml) solution of (h5-C5Me5)Fe(CO)2H
(536 mg, 2.16 mmol) was added n-BuLi (1.49 M, 1.50
ml, 2.2 mmol) at −45 °C (CH3CN–liquid N2 bath).
After stirring the mixture for 10 min, a THF (5 ml)
solution of Me2SiCl2 (520 mg, 4.03 mmol) was added to
the solution at −45 °C. The mixture was stirred for 30
min at −45 °C and then was warmed up to r.t. and
stirred for 1 h. After removal of volatiles under vac-
uum, the residue was extracted with toluene and the
extract was filtered through a Celite pad. The filtrate
was evaporated to dryness to give an orange powder of
9 (655 mg, 1.92 mmol, 89%). 1H-NMR (300 MHz,
C6D6) l 0.92 (s, 6H, SiMe2), 1.47 (s, 15H, C5Me5).
13C{1H}-NMR (75.5 MHz, C6D6) l 9.5 (SiMe2), 12.0,
(C5Me5), 95.9 (C5Me5), 216.1 (2CO). 29Si{1H}-NMR
(59.6 MHz, C6D6) l 87.7.
3.6. Synthesis of (p5-C5Me5)Ru(CO)2SiCl3 (6)
Compound 6 was synthesized by a similar method to
that for 2, using (h5-C5Me5)Ru(CO)2H (336 mg, 1.15
mmol) and SiCl4 (0.44 g, 2.6 mmol). The 1H-NMR
spectrum revealed that the resulting mixture contains 6
and (h5-C5Me5)Ru(CO)2Cl in the molar ratio of 1:4.
The reaction mixture was placed on a silica-gel flash
column and elution was carried out with a toluene–
hexane (1:4) mixture. Removal of solvent from the
fraction afforded a white powder of 6 (95 mg, 0.22

M. Okazaki et al. / Journal of Organometallic Chemistry 645 (2002) 201–205
205
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Acknowledgements
This work was supported by Grants-in-Aid for Scien-
tific Research (Nos. 11740367, 12042210, 12640533,
13440193) from the Ministry of Education, Culture,
Sports, Science and Technology. The authors wish to
thank Nissan Science Foundation, Inoue Foundation
for Science, and Tokuyama Science Foundation for
financial supports.
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